L4: Evolution 2

• What did Theodosius Dobzhansky redefine evolution as in 1937?

  A change in allele frequency in a gene pool
• What are the three main mechanisms of microevolution?

  Natural selection, genetic drift, and gene flow
• Why is testing natural selection important in the context of microevolution?

  It helps to understand how species adapt and evolve over time
• What species did Rosemary and Peter Grant study between 1976 and 1978?

  Geospiza fortis, the medium ground finch
• What does Postulate 1 state about individuals within a species?

  Individuals within a species are variable
• What does Postulate 2 indicate about the heritability of traits?

  Some of the variation in traits is heritable
• How do parents' beak sizes relate to their offspring's beak sizes in Geospiza fortis?

  Parents with small beaks tend to have offspring with shallow beaks
• What does Postulate 3 state about reproduction in a species?

  Reproduction is not random; individuals with favorable variations reproduce the most
• How did the drought affect the finch population on Daphne Major?

  The drought reduced seed availability, leading to selection for larger birds with deeper beaks
• What type of frogs were studied in relation to natural selection after the Chornobyl disaster?

  Eastern tree frogs (Hyla orientalis)
• What selective pressure affected the Eastern tree frogs in the Chornobyl exclusion zone?

  Melanin protects against ionizing radiation
• What are the three Darwinian postulates that have been demonstrated experimentally?

  Individuals within a species are variable, some variations are heritable, and reproduction is not random
• What is the role of mutations in evolution?

  Mutations are the raw materials of evolution via natural selection
• How does a dominant advantageous allele behave in a population?

  It is visible to natural selection as both heterozygote and homozygote, rising rapidly in frequency
• Why does a recessive advantageous allele take longer to fix in a population?

  It is only visible to natural selection as homozygotes, which take longer to accumulate
• What is genetic drift?

  Genetic drift is the change in allele frequencies in populations, even in the absence of natural selection
• How does genetic drift affect allele fixation in a population?

  Genetic drift can fix alleles in a population through sampling error
• What organism is used in Richard Lenski's long-term evolution experiment (LTEE)?

  Escherichia coli
• What significant event occurred in the LTEE regarding the growth rate and cell size?

  In all flasks, growth rate and cell size increased
• How did the ability to use citrate in aerobic conditions evolve in E. coli?

  It evolved through duplication of the gene encoding the citrate transporter, allowing expression in aerobic conditions
• Why is the inability to utilize citrate in aerobic conditions significant for E. coli?

  It is a defining feature that separates it diagnostically from pathogenic Salmonella species
• What is gene flow?

  The movement of alleles between previously separate populations
• How can gene flow occur between populations?

  Through migration of adults and subsequent mating or movements of gametes
• How do gene flow, genetic drift, and selection interact in populations?

  They promote population divergence and can lead to speciation
• What is the definition of a species at the eukaryotic level?

  A population of organisms that can potentially or actually interbreed, giving viable fertile offspring
• How should speciation be regarded?

  As a continuum from varieties to separate species
• What caused the speciation of Hyla versicolor from Hyla chrysocelis?

  Chromosomal duplication during meiosis
• How do the two types of Culex mosquitoes differ in their breeding behavior?

  Culex pipiens pipiens breeds seasonally and requires a blood meal, while Culex molestus breeds continuously and does not
• What significant event occurred in 2016 regarding Geospiza conirostris?

  A male Geospiza conirostris flew into Daphne Major and mated with a Geospiza fortis female
• What is the significance of genomic information in studying evolution and speciation?

  It provides modern comparisons through gene trees from nucleic acid sequences